Reactions of [Ru(CO)3Cl2]2 with aromatic nitrogen donor ligands in alcoholic media

The reactions of mono- and bidentate aromatic nitrogen-containing ligands with [Ru(CO)(3)Cl-2](2) in alcohols have been studied. In alcoholic media the nitrogen ligands act as bases promoting acidic behaviour of alcohols and the formation of alkoxy carbonyls [Ru(N-N)(CO)(2)Cl(COOR)] and [Ru(N)(2)(CO)(2)Cl(COOR)]. Other products are monomers of type [Ru(N)(CO)(3)Cl-2], bridged complexes such as [Ru(CO)(3)Cl-2](2)(N), and ion pairs of the type [Ru(CO)(3)Cl-3](-) [Ru(N-N)(CO)(3)Cl](+) (N-N = chelating aromatic nitrogen ligand, N = non-chelating or bridging ligand). The reaction and the product distribution can be controlled by adjusting the reaction stoichiometry. The reactivity of the new ruthenium complexes was tested in 1-hexene hydroformylation. The activity can be associated with the degree of stability of the complexes and the ruthenium-ligand interaction. Chelating or bridging nitrogen ligands suppresses the activity strongly compared with the bare ruthenium carbonyl chloride, while the decrease in activity is less pronounced with monodentate ligands. A plausible catalytic cycle is proposed and discussed in terms of ligand-ruthenium interactions. The reactivity of the ligands as well as the catalytic cycle was studied in detail using the computational DFT methods. Copyright (c) 2005 John Wiley & Sons, Ltd.